JPH0495788A - Judging method of life for stationary lead accumulator - Google Patents

Abstract

PURPOSE:To easily and accurately detect the service life of a battery by a method wherein an internal impedance of the battery is measured with different frequencies, each value of elements of an impedance equivalent circuit is calcu lated based on the measured impedance, and the calculated value is compared with an initial value, thereby to estimate the life of the battery. CONSTITUTION:An internal impedance equivalent circuit of a battery is formed in such relation as shown in the drawing among an inductance component L of a pole column, a strap, a grid body etc., an electrolyte resistance Rs, a capacity of an electric double layers Cd, a load moving resistance theta, and a Warburg impedance W and the like. A synthesizing impedance of the equivalent circuit calculates at least one value of the electric double layer capacity Cd, load moving resistance theta, Warburg factor and the like, and compares the calculated value with the corresponding initial value. Accordingly, the data related to the state of the battery such as the quantity of the effective reactive substance, surface area or the like can be properly estimated. The service life of the battery can be easily and accurately detected without measuring the discharge capacity of the battery.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for determining the life of a stationary lead-acid battery.

[Prior Art] Conventionally, as a method for determining the life of a stationary lead-acid battery, a method of actually measuring the discharge capacity of the battery and a method of measuring the specific gravity of the electrolyte have been used. The former method of actually measuring the discharge capacity is impractical as it requires a large discharge load and requires time and effort to measure, so the latter method of measuring the specific gravity of the electrolyte is the most common method. It has been done.

[Problems to be Solved by the Invention] However, the cathode absorption stationary sealed lead-acid battery has a problem in that it is difficult to measure the specific gravity of the electrolyte because it is a sealed type.

In view of the above problems, an object of the present invention is to propose a method for determining the life of a stationary lead-acid battery without actually measuring the discharge capacity or measuring the specific gravity of the electrolyte.

[Means for Solving the Problems] In order to solve the above problems, the method for determining the lifespan of a stationary lead-acid battery according to the present invention involves measuring the internal impedance of a lead-acid battery whose lifespan is to be determined using several different predetermined measurements. The measured value obtained by measuring the frequency is synthesized by inductance components such as pole columns, struts, lattices, etc. L1 electrolyte resistance RS % electric double layer capacitance Cd, charge transfer resistance θ, Warburg impedance W, etc. At least one value of the electrolyte resistance Rs, electric double layer capacitance Cd, charge transfer resistance θ, and Warburg coefficient σ is calculated by applying the calculation to the impedance of an impedance equivalent circuit, and the calculated value is applied to each initial value. The lifespan of the battery is determined by comparing it with the value of .

``Function: When the lifespan determination method of the present invention is used, detailed battery information such as the amount and surface area of the effective reactive active material, and the diffusion state of the electrolyte with respect to the active material can be determined from the changes over time in the calculated values of the equivalent circuit components. Information regarding the condition can be estimated appropriately.This allows you to easily and accurately estimate the battery life without actually measuring the discharge capacity of the battery, and even for batteries for which it is difficult to measure the specific gravity of the electrolyte, such as stationary sealed lead-acid batteries. It will be judged.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

The internal impedance of a stationary lead-acid battery is expressed by the impedance of an impedance equivalent circuit as shown in FIG. In the figure, L is the inductance component of pole columns, straps, grids, etc., Rs is the electrolyte resistance, which is mainly the resistance of the electrolyte, and Cd is the electric double layer capacitance at the interface between the active material and the electrolyte, θ
is the charge transfer resistance associated with the transfer of charge between the active material and the electrolyte,
W is the Warburg impedance caused by the diffusion of the electrolytic solution, and these have the relationship shown in the figure to form an equivalent circuit of internal impedance of the battery.

The composite impedance 2 of this equivalent circuit is given by σ, the Warburg coefficient of the Warburg impedance W.
As a function of angular frequency ω, Table 2 (ω) =Rs+jωL+ Figure 2 shows the actual measured internal impedance of a stationary lead-acid battery and the impedance locus (calculated value) of the above equivalent circuit. This is called a Cole-Cole plot.

The battery we actually measured had a capacity of 200Ab, and the measurement frequency range was O, LH! ~I KH2. As seen in the figure, the frequency is 1 to 100H! It can be seen that the measured values and the calculated values of the equivalent circuit match well in terms of degree, and that the representation of the equivalent circuit is appropriate.

Each of the aforementioned electrolyte resistance Rs, electric double layer capacity Cd, charge transfer resistance θ, and Warburg coefficient σ, which constitute the equivalent circuit, will change due to the causes shown in the following table when the battery reaches the end of its life. Conceivable.

Therefore, by applying the actual measured values of internal impedance at several different frequencies to the impedance of the equivalent circuit and calculating the values of each of the above elements, the performance state of the battery can be estimated, and the calculated value is compared with the initial value. This makes it possible to easily and accurately determine the lifespan of the battery.

FIG. 3 shows an outline of a battery internal impedance measuring means, in which 1 is a battery to be measured, 3 is an impedance characteristic detector, and 2 is a potentiostat inserted and connected between the two. A potentiostat has a potentiostat mode in which it measures a current when a certain potential is applied, and a galvanostat mode in which it measures a potential when a certain current is applied. In this embodiment, the potentiostat is used in the galvanostat mode, and alternating currents of several different frequencies with a constant amplitude are applied to the battery 1 from the frequency analyzer 3 via the potentiostat 2.
Connect the current monitor output and voltage monitor output (terminals that output the current passed through the sample and the generated voltage) to the input of the frequency characteristic analyzer 3, and calculate the frequency from the measured values of the current monitor output and voltage monitor output. Find the internal impedance of the battery 1 accordingly.

Next, as a specific example, we conducted an accelerated life test at high temperature on a 200Ah stationary sealed lead acid battery.
FIGS. 4 to 7 show the changes over time of each element calculated using the internal impedance values measured at 11 different frequencies between the two.

The calculation of each element uses the Full Cart method, which is a type of nonlinear least squares method. Specifically, each constant in the equivalent circuit is given an appropriate initial value, and the value of each constant in the equivalent circuit is changed so that the difference between the impedance at each frequency calculated using this constant and the impedance of the measured value is minimized. Then, when the difference becomes less than a certain value, a method is used in which this value is used as the solution. Since this calculation method and calculation formula are well known to those skilled in the art, details will be omitted. Note that this calculation can be easily performed using a computer.

Figure 4 shows the change in electrolyte resistance Rs, Figure 5 shows the change in electric double layer capacitance Cd, Figure 6 shows the change in charge transfer resistance θ, and Figure 7 shows the change in Warburg coefficient σ. j:
? Article. FIG. 8 also shows the change in discharge capacity that was actually measured.

As shown in Figure 4, it is estimated that the electrolyte resistance Rs increases from around 150 days and the electrolyte specific gravity decreases, and as shown in Figure 5, the electric double layer capacitance Cd gradually increases. It is estimated that the reaction area of the effective active material has decreased. In addition, as shown in FIG. 6, 200
The charge transfer resistance θ was estimated from around 200 days, and as shown in Figure 7, the Warburg coefficient σ increased from around 200 days, indicating that the diffusion of the electrolyte into the active material was caused by lead sulfate of the active material. It is estimated that the situation has worsened.

On the other hand, as shown in Figure 8, the actual measured value of discharge capacity is also 20
The capacity rapidly decreased from around 0 days, and reached the end of its life at 230 days. From the above, the battery life can be determined by comparing the calculated values of any or all of the elements of the above-mentioned equivalent circuit with their respective initial values.

[Effects of the Invention] As described above, according to the present invention, the internal impedance of a lead-acid battery is actually measured at various different frequencies, and the values of each element of the impedance equivalent circuit are calculated based on the measured values. Since the battery life is determined by comparing the value with the initial value, there is no need to actually measure the discharge capacity of the battery, and it is easy and suitable for batteries where it is difficult to measure the specific gravity of the electrolyte, such as stationary sealed lead-acid batteries. Lifespan can be accurately determined. Furthermore, from the changes in the calculated values of each element of the equivalent circuit, it is possible to appropriately estimate necessary information regarding detailed battery conditions such as the amount and surface area of the effective reactive active material, and the diffusion state of the electrolyte with respect to the active material. be.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing the impedance equivalent circuit of a stationary lead-acid battery, Figure 2 is a characteristic curve diagram showing the measured impedance value of a stationary lead-acid battery and the vector trajectory of the equivalent circuit impedance, and Figure 3 is the inside of the lead-acid battery. FIG. 2 is an explanatory diagram showing an overview of impedance measuring means. Figure 4 shows the change in electrolyte resistance over time, Figure 5 shows the change in electric double layer capacity over time, Figure 6 shows the change in charge transfer resistance over time, and Figure 7 shows the change in Warburg coefficient over time. FIG. 8 is a diagram of each characteristic curve showing the change in battery discharge capacity over time. L...inductance component, Rs...electrolyte resistance,
Cd...electric double layer capacity, θ...charge transfer resistance W
...Warburg e-impedance. Figure Figure Figure Figure Number of Days Figure Figure Number of Days Figure Figure

Claims (1)

[Claims] The internal impedance of the lead-acid battery whose life is to be determined is measured at several different measurement frequencies, and the measured values are calculated using the inductance components (L
), electrolyte resistance (Rs), electric double layer capacitance (Cd), charge transfer resistance (θ), Warburg impedance (W), etc. Liquid resistance (R
s), electric double layer capacity (Cd), charge transfer resistance (θ),
A method for determining the lifespan of a stationary lead-acid battery, characterized in that the lifespan of the battery is determined by calculating at least one value of and Warburg coefficient (σ) and comparing the calculated value with each initial value.